The overall purpose of the proposed research is to use selected animal models of the human mucopolysaccharidoses to develop and evaluate various therapeutic strategies including enzyme, cellular and genetic manipulations. Inherent in these studies is the characterization of the molecular pathology of each animal model to determine the degree of homology to the respective human disease at the pathologic, biochemical and genetic levels. Four disorders, feline MPS I and VI; canine MPS III and VII, are under study and each has been or will be investigated according to the following scheme: Models are identified, breeding colonies established and the natural history and pathologic manifestations characterized. The enzyme defect is then characterized by purifying normal and residual enzyme and measuring the physiokinetic and immunologic properties of each. Accumulated substrate in various tissues is quantified and correlated with the morphologic pathology. The genetic defect is then characterized by sequencing the normal enzyme, synthesizing appropriate probes, screening cDNA and genomic libraries and comparing the structure and organization of the normal gene to that of the mutant gene. Three therapeutic strategies are evaluated: 1) Enzyme manipulation using compounds which enhance residual enzyme activity, 2) Cellular manipulation using allotransplantation of bone marrow, and 3) Somatic genetic manipulation using mammalian expression vectors to transfer full length cDNA clones into dificient cultured fibroblasts and, with appropriate viral vectors, perform in vivo transfection experiments. The effects of treatment on the clinical and pathologic course of the diseases, enzyme activity and substrate accumulation are evaluated to determine if therepy can prevent, arrest or reverse the disease process.